


Biology

by mansikka



Category: Supernatural
Genre: First Time, M/M, Smut
Language: English
Status: Completed
Published: 2016-04-19
Updated: 2016-04-19
Packaged: 2018-06-02 19:13:13
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 3,103
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/6578998
Author URL: https://archiveofourown.org/users/mansikka/pseuds/mansikka
Summary: <blockquote class="userstuff">
              <p>Dean wants to show Cas how much he loves him the only way he thinks he knows how.</p>
            </blockquote>





	Biology

**Author's Note:**

> If you choose to see this as a standalone, or as a sort of interlude in the Too Far series after Mundane, it is up to you :)

“Cas. I promise you. This has nothing to do with me thinking you're somehow... I don't know. Incapable, or something. Not about that at all.”

 

Cas continued frowning, despite Dean's reassurances.

 

“Cas,” Dean repeated, smiling a little wider as he wrapped his fingers around Cas' waist and pulled him until he was pressed back against Dean's chest. He dipped his head down so that he could trail kisses up Cas' neck, smiling even more as Cas hummed in approval and tilted his head to the side to give him more access.

 

“Sometimes you do speak to me as though I know nothing of anything, Dean,” Cas grumbled, although by now it was more than half-hearted.

 

“I don't mean to, Cas,” Dean whispered, pressing a firmer kiss just in the spot behind Cas' ear that he'd done enough times now to anticipate the little moan he got from him as reward. “I... I know there's some stuff you don't know-”

 

“Pop culture,” Cas blasted out in a gasp that lost its tone of protest as soon as Dean ducked down and bit his earlobe.

 

“Yeah,” Dean agreed, purposely breathing out in Cas' ear and smiling at the way he sucked in a breath. “That. But. I know. I don't mean to... I don't know. Belittle you, Cas. And... I'm sure you know... all about _this_ kind of stuff. Biology and... yeah, that. You kinda rebuilt me from the inside out so...”

 

“I did,” Cas agreed as he reached to slip his fingers between Dean's where they pressed into his hips.

 

“I just... let me do this for you, Cas. I want to. I wanna show you. You know. How much I...”

 

Dean's words trailed away from him, but Cas knew enough to not need the sentence completing. With a gentle squeeze of his fingers over Dean's he spun himself around, wrapping his arms around Dean's neck and leaning into him.

 

“You know, Dean,” Cas began, nuzzling his nose against Dean's chin, “There are other ways to show-”

 

“I know, Cas,” Dean cut him off, ducking down and kissing him quickly. “I know. But. This. This is, uh... a very human way of showing you how I feel. You know? I... don't really know any other way.”

 

Cas smiled wide then, laughing to himself. “I... do not believe the angel method of showing affection would … It might be a little overwhelming for you. Or possibly even fatal,” he admitted, his eyes growing wide for a moment as he thought about that.

 

“Cas,” Dean whispered, swallowing awkwardly and raising his hands to cup Cas' face, “This is... a lot more than just _affection_ , Cas. It's... you know it's... I...”

 

Cas tilted his chin, closing the the gap and kissing him. “I know, Dean.”

 

Dean shuffled closer, pressing their foreheads together, still cupping Cas' face. “And... you know. I want you, Cas. I want this. With you,”

 

Cas let out a deep, pleased sigh and nodded. “I want this too. You,”

 

Dean sighed himself, closing his eyes and his face relaxing in his relief. “Thank you,” he said, smiling with gratitude. “It's... it's just taken us so long to get here. I wanna do this right.”

 

Cas nodded, feeling a little overwhelmed by the unexpected rush of emotion he felt to hear Dean's words, so remained silent, closing his eyes as Dean began a trail of featherlight kisses over his face. He turned his face up in acceptance of them, smiling when Dean rubbed their noses together, sighing as the kisses trailed over to his ear, and sucking in a breath as gently, Dean bit lightly just behind it, before continuing the trail along his neck.

 

Cas tilted his head, giving Dean full access to him there, his own hands by now having already slid down Dean's chest to wrap around his waist. Dean's hands shifted, fingertips brushing gently down the length of Cas' throat before his palms flattened out to slip across and over Cas' shoulders.

 

Since this thing between them had developed, Cas had taken to making himself a little more at home when he was in the bunker. His trenchcoat and jacket came off almost immediately upon his arrival, and his sleeves rolled up past his elbows in a way which really had Dean's attention more than he ever really thought such a thing would.

 

But feeling the sheer strength of Cas through just the thin shirt covering his skin, and knowing he'd be the one who got to feel that under his own fingertips soon, had Dean swallowing repeatedly and breathing shallowly and shakily reaching for Cas' tie.

 

He unknotted it slowly, keeping his eyes firmly fixed on Cas' the entire time as he slipped it around and off from his neck. His fingers reached to unbutton his shirt, grazing his thumb lightly against the skin of his throat and letting out his own gasp that echoed Cas'.

 

Cas loosened his light grip on Dean's waist as Dean rucked up handfuls of the bottom of his shirt to pull it free of his pants, before continuing his slow unbuttoning that he now followed up with kisses all the way down his chest. Dean smiled as Cas' muscles contracted in reaction to his touch, kissing his way back up and claiming his mouth as he gently slid his hands under Cas' shirt, over his pecs, up and over his shoulders and finally pushed the shirt off of him entirely, holding on to Cas' waist with one hand as he threw the shirt behind him.

 

Dean couldn't help himself; his fingers stroked over every inch of skin now on show before him, even to the point of running his fingers down from Cas' shoulders to his wrist, and discovering on that route that Cas was ticklish behind his elbow on his upper arm. Grinning with this new information, Dean lightly tickled him there again, with Cas' only objection a mild intake of breath that was soon kissed away.

 

Dean walked behind Cas, pressing kisses into his shoulder, down over his shoulder blades and into the dip between them before going back up the other side. He wrapped a hand around to splay over Cas' stomach and bit down lightly at the base of Cas' neck, smiling there and replacing his teeth with his lips as he heard Cas gasp out and felt him press back into him.

 

Cas brought his own hands up to cover Dean's, and Dean slid his other on top of Cas', pulling him back flush against him and pressing another trail of kisses down along his neck and to his shoulder.

 

“Doin' okay there, Cas?” he mumbled into his neck, smiling at the soft mm of agreement.

 

Dean continued his circle moving around Cas, kissing his way as he went. When they were back chest to chest, he quickly shrugged out of his own clothes, showing only the slightest flush of embarrassment as he did. He then pressed his skin against Cas', letting out a soft moan that sounded a lot to his own ears like wonder; which he supposed it was, really, after imagining the feel of Cas against him for so long.

 

Cas' own breathing became a touch more erratic, his hands flitting by Dean's sides and slowly drawing up and around his back as Dean repeated almost the same patterns on him, covering as much skin as possible.

 

With a gentle kiss and nudge to the side of his mouth, Dean wordlessly asked for entrance, sliding his tongue in in a way that was sensual instead of loaded with want; although that was there too, both of them hard and letting out little groans when they pressed their hips into one another.

 

With stuttering fingers Dean slid open the clasp on Cas' belt, unpopped his button and unzipped his fly, all without breaking that kiss. Dean slid the tips of his fingers beneath the waistband of Cas' boxers and pulled, swallowing the choking sound Cas let out at the feel of himself springing free. Dean continued pushing them down, smiling as Cas seemed to shimmy his hips to help him then rested his hands on Dean's shoulders before stepping out of his clothes and kicking them to one side.

 

“Cas,” Dean breathed, knowing it came out nothing short of irreverent as he took a moment to steady his breathing, resting his forehead against Cas'. He raised his hands to cup Cas' face again, kissing him softly and smiling into his lips as he felt Cas' own hands drifting up his chest, his fingers tracing light circles over his nipples and soon turning that smile into a moan.

 

As Cas continued his exploration of Dean's chest and back, Dean let his head fall forward on to Cas' shoulder, sighing at the feel of Cas' hands on his skin. A little later, he drifted his hands down to slot his and Cas' fingers together as he pressed the full length of his body up against Cas' and met his answering moan.

 

Their hands stayed curled together by their sides as they kissed, skin on skin, leaking cocks pressed between them and nothing but the occasional unconscious rocking of their hips against one another doing anything to move things along.

 

Dean released his grip on Cas' fingers, running his fingertips up Cas' arms and unable to keep the huge smile from his lips as Cas grumbled at the tickling there once again. Dean circled his arms around Cas' neck, nuzzling into him as Cas' hands found his hips and slid around to cup his ass. He continued his nuzzling and light kisses as Cas' hands continued their exploring, and Dean did nothing to prevent the sighs of contentment that spilled out of his lips from time to time as he did.

 

Dean let his hands drop, drifting down Cas' chest again before moving around to mould around Cas' ass as he rucked back up against him, moaning out hard as he stopped to make a quick adjustment between them to line their cocks up together before moving his hand back around. Cas' own moan reverberated against Dean's collarbone, which just made him rock that little bit harder.

 

Dean smiled to himself again when he felt his own knees begin to tremble, and gently rested his hands on Cas' hips to guide him backwards towards the bed. When Cas' legs bumped up against it Dean stopped, holding on to Cas' fingers and stepping back for a moment to let his eyes linger over him with an ever-widening grin of appreciation.

 

With more gentle nudges Dean guided Cas on to his back, angling himself so that he could reach down between them to wrap them both in his hand. His smile grew wider still, as Cas answered his thumb stroking over their heads with a soft groan and dropped his head back for a second, before lifting it again to watch Dean's hand at work.

 

“How's that feel?” Dean whispered, leaning forward and pressing a kiss to Cas' forehead as Cas continued watching them. Cas raised his eyes, looking back at Dean a little startled.

 

“I... I did not expect... Dean,” he breathed eventually as though all other words had escape him. Cas' hands clenched and unclenched by his side, and Dean smiled his way into another kiss.

 

“Guess there's knowing and there's... _knowing_ ,” Dean smirked, earning himself the surprise of Cas rolling them over, straddling his lap, and leaning over him until his mouth was barely an inch above Dean's.

 

Cas pulled back to look at him tersely for a second, then rolled his hips down on Dean and dropped his mouth down for another kiss, insistently flicking his tongue against Dean's lips until he parted them for him.

 

Dean rested his hands for a moment on Cas' knees then stroked upwards until his fingers were curled around his hips, happy to let Cas set the pace of their lazy rolling together. When Cas' breath became more erratic Dean ran his hands up Cas' sides, pulling his mouth away from Cas' to kiss his way down his neck as he gently rolled them back over.

 

Dean continued his kisses, all along Cas' neck, down to graze a nipple and smile there against him as Cas arched up at the feel of it, then back up to claim his mouth briefly.

 

“Can I, Cas?” he whispered against his lips as he rested their foreheads together. “I know you know the... uh... mechanics of this, but. It's... I need to do this right. So it feels-”

 

“I trust you, Dean,” Cas assured him, arching his neck up and pressing their mouths hard together.

 

Cas kept his eyes firmly on Dean as he nodded, shifted away for a moment to slide open the drawer in the cabinet beside the bed, and rolled back with a bottle in his hand. Dean's eyes darted up at his for a second and a blush covered his cheeks; it was pretty obvious that despite all of Dean's gentle questioning and non-pressured suggestions, he'd been prepared for this, and had been thinking about this, as though there was a sense of inevitability to it happening.

 

Cas smiled at him warmly then, because perhaps there always had been.

 

Cas watched as Dean crawled between his legs ,and willingly let him angle them so that his feet were flat on the bed and his knees splayed. He watched, as Dean uncapped the bottle and drizzled the clear gel over his fingers, then looked up at him with a shuddering breath.

 

Dean positioned himself so that he could stroke Cas open yet still maintain eye contact with him, and caught every gasp, moan, and fluttering of Cas' eyelids as he did. The look on Cas' face at the first feel of Dean gently pressing that first finger in was incredible, with shock soon replaced by the surprise of enjoyment, and then by the demand for more.

 

Cas rolled unconsciously down on Dean's fingers, choking out a whine as Dean nudged against his prostate, and spread his legs even wider in invitation. His eyes grew rounder still as Dean lined himself up and slowly pushed inside him, letting out his own irreverent breathing of Dean's name as he filled him whole.

 

Dean had promised himself that if he ever got to be this lucky, that if he ever got to be with Cas like this, that he'd commit every breath and sound to memory. But there was just so much for him to take in, with each one of those noises that he thought couldn't be any better replaced by another, and his fantasies about getting Cas ready for him like this all but disappeared at the feel of actually being inside him.

 

As Dean slowly stroked in and out of him, Cas hooked his arms around Dean's neck, fixing him with a look of such adulation that he couldn't look away. Cas' mouth remained slightly gaped open, part in acceptance of the frequent kisses Dean dropped on him, and part as though he really couldn't believe how good this really felt.

 

Dean was lost, in the feel of tight heat as he thrust in and the urge to keep chasing that down every time he pulled out. Cas arched with him, dragging him deeper, seeming to squeeze and spasm around him harder as he continued to let out the most delicious of noises beneath him that Dean knew he'd never tire of hearing.

 

Dean fought against his instinct to pick up speed, breathing shallowly and trying to focus his attention on watching Cas' reactions. Cas' own breathing grew more choppy and his mouth opened and closed a little in time with Dean's thrusts, until Dean flicked his tongue inside with the same rhythm. Cas' answering moan did nothing for Dean's self control, and his hand reached between them to stroke Cas instead, finally letting himself speed up.

 

Cas writhed beneath him, hands falling against the mattress and staring up at Dean open-mouthed as he pounded into him, propped up and straining on one arm as he pressed himself harder into Cas at just the right spot and watched his head press back heavily on the pillow. With one final grazing of his thumb over Cas' slit Dean watched, and felt, as he arched up against him and came, looking down at himself in surprise at the mess he made.

 

Dean paused only for a moment to enjoy the look on Cas' face then let himself fall forward a little, bracing himself now with both hands before thrusting in hard two, three more times, and coming himself.

 

Cas arched up a little again as Dean came, his eyes blown wide as he watched. He let out a soft huff of exertion as Dean fell forward on top of him before quickly bracing himself on his forearms to take some of his weight off of Cas' chest.

 

Cas' fingers idly traced in long lines down Dean's side, and Dean's smile split wide and happy as he leaned forward to nuzzle against him. Slow, lazy kisses followed with Dean still inside him as he grew soft, in no hurry to move at all.

 

“You okay, Cas?” Dean mumbled against his lips, a kiss to his cheek and his nose nudged against Cas' as he pulled his face back slightly to gauge Cas' expression.

 

Cas nodded, his face sleepy with contentment, which did nothing but make Dean smile even wider. “I did not expect it to feel... like _that_. Or that I would be... _tired_ ,” he said, eyes fluttering shut repeatedly.

 

“S'ok, Cas,” Dean said, nuzzling against him again before kneeling back upright. At Cas' reaching for him with a whine of complaint for moving, Dean bent back down to kiss him, then kneeled his way off the bed and grabbed his t-shirt to wipe Cas down. He laid back down beside him, grinning to himself as Cas rolled over on to his side, then dragged Dean with him so that he was on his back once again.

 

With absent fingers Cas reached out and stroked through Dean's hair, before wrapping his arms around him, dropping a kiss on the top of his head, and letting his head fall back on the pillow. Dean propped his head up on his chin to watch with surprise, amusement, and not a little bit of smug triumph as Cas fell asleep.

 

Dean stretched himself up long and languidly against him in contentment, then let his head fall to Cas' chest and pressed lazy kisses there until he fell asleep himself.

 

 


End file.
